A driving control device of a motor such as a brushless motor energizes an armature coil of each phase of the motor in accordance with a position of a rotor being rotated. Therefore, the driving control device of the motor uses a rotational position detector such as a Hall sensor, for example, and detects a rotor position, based on an output signal from the rotational position detector. Then, the driving control device of a motor sets a pattern (energization pattern), which is energized to each phase of the motor, based on the detected rotor position, and thus it controls the rotation of the rotor.
Also, the driving control device of a motor performs advanced angle control to match a phase of an induced voltage and a phase of current of the motor in the armature coil in order to correct a relative error of an attachment position of the Hall sensor or to maximize torque of the motor.
When the driving control device of the motor performs the advanced angle control, if the motor is activated with an energization pattern highly deviated from an appropriate advanced angle position, an unstable operation such as rotation of the motor in an unintended direction may be caused. Here, JP-2009-268225 discloses a control device that switches energization patterns when activating of a motor and after the motor reaches a predetermined rotation speed, so as to stabilize rotation driving upon low speed rotation just after the motor is activated.
The abstract of JP-2009-268225 describes, as a problem to be solved, “to provide a brushless motor control device capable of stabilizing rotation driving with simple control, particularly rotation driving upon low speed rotation just after activation”, and, as a solving means, “a drive timing generation unit 16 generates a normal energizing timing and a 120-degrees advanced angle energizing timing, based on a rotational position (detection signals from Hall elements Hu, Hv, Hw) of a rotor 10a, and a control unit 17 generates a delay amount relative to the 120-degrees advanced angle energizing timing in accordance with a rotation speed of the rotor 10a. When the rotation speed of the rotor 10a is below a predetermined rotation speed, the control unit 17 performs rotation control under the normal energizing timing. When the rotation speed of the rotor 10a is the predetermined rotation speed or greater, the rotation control is switched to rotation control under the advanced angle energizing timing, in which the delay amount is reflected.”